In general, a touch pad is an input device that may sense a location of a contact point by contacting another object such as a finger or a pen on a pad location of a point corresponding to a screen of a display device. In recent years, the touch pad has been used as a representative method instead of a mouse of a notebook computer. A touch screen is a device that a user contacts a picture or a character visually displayed on a screen by hand or with a pen to perform a command by attaching a transparent sensor having the same size as that of a display device to a screen coordinate and a contact point coordinate to correspond to each other.
The types of the foregoing touch panel and touch screen may be classified for each medium sensing a contact signal. There are a resistive type, a surface acoustic wave (SAW) type, a capacitive type, and the like as representative types of the touch pad or the touch screen.
In a resistive type touch screen panel, insulation bars are provided between a glass or transparent plastic plate and a polyester film using a resistive material at predetermined distance such that the glass or transparent plastic plate and the polyester film do not contact in such a way that the resistive material is coated on the glass or transparent plastic plate and the polyester film is covered thereon. When the user touches the resistive type touch screen panel, a resistance value varies and an applied voltage also varies due to a physical change in the insulation bars. A contact location is recognized according to the variation in the applied voltage.
The SAW type touch screen panel includes a transmitter, a reflector, and a receiver. The transmitter generates an ultrasonic wave and is attached to one corner of glass. The reflector reflects a sound wave and is spaced apart from the transmitter by a predetermined distance. The receiver is attached to another side of the reflector. When a panel contacts an object such as a finger preventing the sound wave, some ultrasonic wave is absorbed. The SAW type touch screen panel uses a method of calculating a location where the change occurs and simultaneously recording a contact location.
In a capacitive type touch screen, when both sides of glass are coated with a transparent special conductive metal and a voltage is applied to four corners of a screen, a high frequency is generated on a surface of the touch screen. In this case, if a conductive object such as a user's finger contacts on the capacitive type touch screen, a high frequency component become low. Such digital data is analyzed by a controller to find out a contact location. The method is not influenced by external factors and a panel has high transparency and thus is the most frequently used technology.
An infrared type touch screen uses straight attribute of light, and is a technology using an attribute that is blocked and is not advanced when there is an obstacle. In a basic structure of a panel, a plurality of infrared light emitting diodes being an emission device and a photo-transistor being a receiving device are disposed to face each other, and an optical grating frame is made and mounted around a front cover of a monitor. An object such as a finger touches the infrared type touch screen, because light is blocked and is not sensed by a photo-transistor of an opposite side, a touched location of a cell is recognized.
Because only on/off of an existing touch pad is sensed based on an input signal, whether an operation is performed suited to the intention of a user can be known by only a change in a corresponding picture or button. Accordingly, because an error with respect to a desired operation of the user can be appreciated according to presence of a function operation, delay occurs for some time. When the touch pad is used by only on/off input as described above, sensitivity of the touch pad may not be adjusted, operation erroneously performed cannot be prevented when a key is strongly input.
An existing touch screen touches a screen based on a screen, namely, a panel to recognize a location, and may perform a multi-touch function, a drag function, and the like in some cases. However, the multi-touch function, the drag function, and the like are performed by a method capable of being used in a plane, and thus it is difficult to implement a previous resolution and precision in an irregular side. As in the touch pad, because the existing touch screen recognizes only on/off input, namely, touch, the touch screen may cause an erroneous operation of desired input.
Such problems occur because the touch screen cannot recognize pressure which the user applies.